Synchronous rectification has been widely employed in power converters to minimize the power dissipated in conducting diodes. Synchronous rectification is implemented by paralleling conducting diodes with a switching device that has a lower voltage drop and can be controlled in such a manner as to conduct synchronously with the diode. Broadly, a direct current-to-direct current (DC/DC) power converter is any power circuit configuration that has a direct current input and a direct current output and utilizes a controlled switching action to convert from one DC voltage to another DC voltage. The input and output power may or may not be electrically isolated. Synchronous rectification control is usually implemented by analog circuits that operate in real-time or with dedicated integrated circuits (ICs) that sample the diode voltage/current at a high speed. These types of circuits can be either adaptive or predictive. Adaptive control systems maintain synchronous operation in response to changing operating conditions and changing component values. Predictive control systems use the previous switching information to control the present operation. In either case, the diode current and/or diode voltage is monitored and a synchronous switch is turned on whenever the diode would be conducting and turned off whenever the diode would not be conducting. Sensing currents and voltages can be done very fast in analog-based circuits and can also be accomplished in microprocessor-based designs if sampling is done at a very high rate.
What is needed is an advancement in the art of synchronous rectification that eliminates the need for sensing the diode current and/or diode voltage and that is adaptive and predictive.